XML Sitemap plugin -- problems with mapped domains reverting to subdomains

I have a serious problem with the XML Sitemap plugin and the domain mapping plugin.

Sitemaps on blogs for which I have a mapped domain keep reverting to the subdomain instead of the mapped domain, resulting in indexing errors from the search engines.

If I publish a post and a comment on an affected blog, the sitemap will temporarily switch back to showing the proper mapped URLs, but then at a later date, will revert to the subdomain URLs.

I haven't had any issues with the pages or posts themselves and their domain paths, just with the xml plugin. Help!